Let's discuss short shifters and synchros

Do short shifters increase synchro wear and tear? This is a heavily debated topic on every tuner forum. It may not even be a concern for our gear boxes. But this IS Ford here. I'll do my best to explain it all. I'm leaving out a bunch of details and nuances for simplicity sake (or cuz idk lol). Maybe as a group we can decide if a short shifter can indeed expedite synchro wear and tear. Take this ALL with a large grain of salt lol This is written to spark debate, not state a fact in stone! This is just my understanding of a modern manual transmission.

The synchros move at road speed (or lack there of) because they are directly connected to the OUTPUT shaft. The gears (1-6) themselves are also on the output shaft but spinning independently from it on needle bearings. In other words, the forward gears are NOT directly connected to the output shaft, at all.

The gears are spun via engine power brought into the transmission on the INPUT shaft. It has its own set of directly connected gears that are meshed (in contact) with the gears on the output shaft. So the moment you turn on your car, the gears are freely spinning on thier needle bearings on the output shaft at a given ratio of engine speed but not engaged. The synchros aren't moving yet as they move with the wheels via the output shaft (for simplicity sake)

FUN FACT: Pressing the clutch disengages the input shaft from the engine. At that point the gears slow down on their needle bearings, depending on just momentum. If your car is moving, the synchros continue to rotate at road speed.

Simply put, when a gear is selected, the shift fork acts on the synchro sleeve, sliding it's beveled dog teeth over a set of beveled teeth on the selected gear, locking that gear to the output shaft and transferring the engine rotation at the selected gear ratio to the wheels. Remember, the gear is rotating at a reduced speed (clutching in disengaged engine input briefly) and the synchro is moving at full road speed. The thing to understand is that they move at different speeds until synchronized and fully engaged.

Let's get into more detail...ignore starting from a stop as we are discussing short shifter which are used while moving.

One of the jobs of a synchro assembly is to match the speed of the selected gear (moving at a some factor of engine speed) to the speed of the output shaft (wheels). It begins this process with a brass blocker ring. It has a conical inner surface that mates with the conical surface of the forward gear on the ouput shaft. Think of it as a male/female realtionship. The male being the gear. As the shift fork moves the synchro sleeve toward the selected gear, the ring is literally pressed onto the gear and via friction, begins to match the speed of the gear to the synchro assembly that is spinning at road speed.

Once the speed of the synchro assembly and the forward gear are beginng to sync, a series of beveled teeth on the ring and on the gear start to align. They don't have to align perfectly and frankly, at the RPMs they operate, odds are they will never perfectly align every shift. For that reason there's a bit of play designed into the movement of the ring. Also, the teeth are at an angle (beveled) allowing them to kind of bump and glide. This facilitates the many teeth of all of these surfaces to mesh smoothly even though they may not align perfectly.

At this point, the gear is still not engaged. The inner dog teeth on the synchro sleeve have to manuever the beveled teeth on the block ring and the gear itself. This is what ultimately locks the gear to the shaft, engaging it. The sleeve will only engage when the teeth on the gear and the blocker ring are in close enough alignment to allow the dog teeth inside the sleeve to bump and glide over BOTH the blocker ring and the selected gear.

It's hard to explain but picture it. You have teeth on one side spinning and a whole other set of teeth spinning on the other side. They have to somehow mate without the whole thing shattering into bits. Having bevels or angles in the teeth allows them to shift and move and grove however they need to so that the sleeve can lock the gear to the output shaft without grinding. An engineering marvel really.

FUN FACT: I'm a bit fuzzy on this detail but another job of the synchro is to block the gear change (blocker ring) if the delta between the input and output shafts is too great, usually due to ratio. For instance, try going into the 2nd at highway speeds and the synchro will prevent it.

HOW COULD A SHORT SHIFTER INCREASE SYNCHRO WEAR?

Parts of the synchros are brass and designed to wear. They are of a softer material than the gears themselves. It's a part of how they effectively smooth out gear changes. Remember, the different speeds are matched up via the friction applied on the gear by the blocker ring found on the synchro assembly. A synchro needs time to accomplish this miraculous feat. I would think that the chosen friction materials for a given tranny all work within a given set of design paramaters. For arguments sake, say a friction material is designed to sync a gear within 5-7ms or whatever. It's now being asked to do the same thing in 25% less time via a short shifter. This will increase the odds of a grind, at worst, and at best increase the wear on the brass beveled teeth and sleeve as we don't give the teeth time to come into their designed and expected alignment.

FUN FACT: You know those times when you are at a light and it won't go into 1st, so you clutch in and out then it goes in no prob....synchro is not aligning on the first attempt. Disengaging and re-engaging the input shaft quickly changes the rotation of the input shaft, changing the rotation of the gear, allowing a different alignment of the teeth and so the the gear goes in the second time. If you find yourself doing that ALL the time, you may have a worn synchro.

For those who note that an SS like Coolerworx works on the mechanical arm of the shifting mechanism, you are correct. But you are missing a critical point. The mechanical arm you speak of is directly acting on the shift rods whose sole purpose in life is to act on the shift forks...and as mentioned above, the shift forks move the synchros and lock the gear to the output shaft. Shorten that mechanical action by 25% and you reduce the time it takes to act on the rod, that acts on the fork, that wears down the synchro...Theoretical, but technically possible and imo a sound argument.

And that is why I do use an SS but only at it's lowest setting...

What are your thoughts FiST'rs?

I would like to add my 2¢ worth.
I added both the Mountune and Boomba short shifters to my FiST as soon as available.
I put over 50K miles on the car before selling without ANY problems with the trans or clutch for that matter.

I also put short shifters on every manual trans cars I have owned and there have been many.
I never had issues with synchros, except due to MY fault of trying to shift without using the clutch.
Maybe I was just lucky.

I've had zero problems on my short shifters on any car I've owned. That includes my 97 Mustang Cobra, the FiST, a GD STi, DC Integra R and others. I also rev-match EVERY down shift I make, even on the street. At this point its just a habit.

As for 1st gear and aligning synchro, I was taught that you really only need 1st when you are coming from a complete stop. AutoXers will disagree, but for normal spirited driving and even track days, I have never had to use 1st anywhere but coming out of the pit lane.

I will also add another note of what NOT to do.
Once driving my '65 Mustang, purpose built track car.
Down the main straight of Willow Springs International Raceway (Big Track), at over 140 MPH entering turn one.
I down shifted from 5th to 1st (instead of 3rd).
I did not hurt the trans however, I did blow the clutch ALL to HELL.
I do suggest that no one do this.

I've never had any probs either. I was just looking at the possibility. Does it even make sense that it COULD have a negative effect on synchros? A quick Google search turns up tons of forums discussing the topic without any agreed conclusion...same here I guess lol

Any grinds ive gotten were from my lack of coordination for a moment. That said im over having a short shifter in my car, as it introduced some vague "didnt feel like its in gear, but it is" feeling in the shifter itself.

I got a question but first a quick background I'm a Honda guy I've been driving the same Honda for 8 years, Honda Accord coupe 2008 five speed. I've recently purchased my Ford fiesta ST I don't know what's wrong with me but when I shift from 1st to 2nd everything is good but from 2nd to 3rd while I a slight rush I miss that gear all the time I always end up in 1st again or 5th gear smh, does anybody think a short shifter will give me better accuracy when shifting??

Short and solid shifters do tend to give one a better accuracy feel. Yet like PunkST has stated and I have felt it in a few cars with short shifter. Though the shifter feels more accurate, I do get the feel that its not quite locking into the gear. In part I think that is due to the shorter travel .

@Tom_FordFiestaST. Has the rear motor mount been swapped for an aftermarket one? The stock one has too much play for a turbocharged engine

Best bang for buck ive found is the shifter cable bracket bushings under the hood. Its given the car the most direct feel without risking damage to synchros from a short throw, and leaving stock shifter base bushings in the car keeps anyone from wrecking the plastic tower. Again this is just my experience from driving the car.

Would worn synchros make it gradually more difficult to get into gear? I've heard people talk about how shifting in this car is smooth as butter and mine never has been (bought it used with 100k). There's like a threshold of resistance before the shifter plops into place with almost every gear. If I press lightly up against it, it eventually gives way, so it's not necessarily related to the amount of force I apply.

Worn synchros from ham fisted shifting and forcing it into gear. Will make it difficult to get into gear, worn fluid will as well, busted synchros make it jump out of gear on load iirc.

No the rear mount is still stock I bought the car used 58,000 MI on it. I'll try putting that rear mount on and probably the side mounts as well. I know about the short shifter bracket you're talking about it's pretty easy to pop on as well in fact I'll do both at the same time.

As for mounts i only have a poly rear mou t and a poly passenger mount. I left the oem rubber upper trans mount. Less vibration, and still has improved performance. I did all 3 on my old focus and using the A/C in summer was like turning on a paint mixer. Lol.

Worn synchros can def cause what your experiencing. I would first do a swap and fill with Ford OEM fluid and see how she feels. I did the 2L fill everyone was talking about a few months ago. Greatly improved shifting. I will now do it every 15-20k. It's so cheap and easy, why not.

@PunkST That vagueness in shifting makes sense. Not everyone has the sensitivity to feel subtle issues like that. I def do which is another reason i set my SS at 15 instead of 25%. I suspect that too short a throw is not seating the synchro fully. And i'm talking mm's here. But when you can 'feel' an oil change is due or it's time for plugs, you can also feel that not so engaged weirdness in the shifter.

I installed the shifter base bushings, love'em, and will install the shifter bracket bushings while replacing the two worn upper motor mounts with fresh OEM mounts sporting PowerFlex inserts. Shifting will be magical when it's all done.